Alkylation of aromatic hydrocarbons



H. s. BLOCH Y ALKYLATION oF AROMATIC HYDRocARBoNs Filed Fb. 21. 1957 May 19, 1959 /N VEA/TOR Herman S Bloch A Tron/vers:

United States Patent() ALKYLATION F AROMATIC HYDROCARBGNS Herman S. Bloch, Skokie, lll., assignor, by mesne assignments, to Universal Oil Products Company, Des Plaines,

` lll., 'a corporation of Delaware Application February 21, 1957, Serial No. 641,635 22 Claims. (Cl. 260671) intermediate, which ethylbenzene is utilized in large quantities in dehydrogenation processes for the manufacture of styrene, one starting material for the production of some synthetic rubbers. Another specific object of this invention is to produce alkylated aromatic hydrocarbons Within the gasoline boiling range having a high `antiknock value and which may be used as such or as components of gasoline suitable for use in airplane or automobile engines. A further specific object of this invention is a process for the production of cumene by the reaction of benzene with propylene, which cumene product is oxidized to form cumene hydroperoxide which is readily decomposed into phenol andacetone. Another object of this invention is the production of para-diisopropylbenzene which diisopropylbenzene product is oxidized to i terephthalic acid, one starting material for the production of some synthetic bers. Still another object of this inlvention is to provide a process for the introduction of alkyl groups into aromatic hydrocarbons of high vapor pressure at normal conditions with minimum loss of said high vapor pressure aromatic hydrocarbons and maximum utilization thereof in the process. 'This and other objects of the invention will be set forth hereinafter as part of the accompanying specification.

In prior art processes for the alkylation of aromatic hydrocarbons with olefin hydrocarbons, it has been disclosed that it is preferable to utilize molaiexcesses of aromatic hydrocarbons. In such processes it is` generally preferred to utilize greater than 2 mols of aromatic hydrocarbon per mol of olen hydrocarbon, and in many cases, for best reaction, it is preferred to use 3 or more mols of aromatic hydrocarbon per mol of olefin hydrocarbon. This has been found to be necessary to prevent polymerization of the olefin hydrocarbon from taking place prior to the reaction of the olen hydrocarbon with aromatic hydrocarbon. While generally satisfactory 4processes have resulted from the utilization of such molar 'excesses of aromatic hydrocarbon, a problem has arisen `when these molar excesses are utilized in connection with -Jthe alkylation of aromatic hydrocarbons of high vapor lminor quantities in various refinery gas streams containing major quantities of other gases such ashydrogen, nitrogen, hydrogen sulfide, and hydrocarbons such as Mice methane, ethane, propane, n-butane, and isobutanej It hasbeen suggested in the prior art that the aromatic hydrocarbon to be alkylated can be utilized in a gas-liquid absorption zone for the absorption of the `olefin hydrocarbon from such gas streams. When the aromatic hydrocarbon thus utilized has a high vapor pressure at normal conditions, concurrent loss of the aromatic hydrocarbon is observed due to the vapor pressure of the aromatic hydrocarbon in the absorption zone, which aromatic hydrocarbon uis carriedffromthe absorption zone along with the unreactive gases which the prior art suggests can be vented from the absorption zone. This problem is accentuated further as the amount of aromatic hydrocarbon is increased to provide the desired molar excess g in Erelation to the olefin hydrocarbon, particularly normally gaseous olen hydrocarbon. Thus, as the molar quantity of aromatic hydrocarbon is increased to prevent polymerization of the olen hydrocarbon reactant, this problem becomes more acute. By means of the process of the present invention', this and other disadvantages inherent in presently utilized processes can be overcome.

In one embodiment the present invention relates t6 a combination process which comprises absorbing in an absorption zone a normally gaseous olein hydrocarbon from a gas stream in a polyalkylaromatic hydrocarbon at a pressure of from about 100 to V2000 pounds per square inch, said polyalkylaromatic hydrocarbon being characterized by having a higher boiling range than the desired alkylated aromatic hydrocarbon product of the process, passing to a stripping zone said absorbed olefin hydrocarbon and said polyalkylaromatic hydrocarbon,

A` removing from the process as bottoms from vsaid stripping zone at least a portion of said polyalkylaromatic hydrocarbon, passing to an alkylation zone as an overhead from said stripping zone said olen hydrocarbon in admixture with a molar excess based on said normally gaseous olen hydrocarbon of aromatic hydrocarbon to be alkylated, alkylating in the alkylation zone said aromatic hydrocarbon with said olefin hydrocarbon in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating fromeluents of saidv alkylation zone unreacted aromatic hydrocarbon, desired alkylated aromatic hydrocarbon product, and higher polyalkylaromatic hydrocarbon, recycling the unreacted aromatic hydrocarbon for reuse in the process, recovering alkylated aromatic hydrocarbon as product from the process, and recycling said higher boiling lpolyalkylaromatic hydrocarbon to the absorption zone as aforesaid.

Inv another embodiment, the present invention relates to a combination process which comprises absorbing in an absorption zonela normally gaseous olen hydrocarbon from a gas stream in a polyalkylbenzene at a'pressure of from about to about 2000 pounds per squareinch, passing to a stripping zone said absorbed olefin hydrocarbon and polyalkylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyalkylbenzene, passing to an alkylation zone as an overhead from said stripping zone said olefin hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of benzene to be alkylated, `alkylating in the alkylation zone said benzene with said olefin hydrocarbon in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from efuents of said alkylation zone unreactedbenzene, monoalkylbenzene, and polyalkylbenzene, recycling the unreacted benzene for-reuse in the process, recovering monoalkylbenzene as product from the process, `and recycling said polyalkylbenzene to the absorption zone as aforesaid.

In still another embodiment, the present invention relates to a combination process which comprises absorbolefin hydrocarbon and said polyalkyltoluene, removing jfrom the process as bottoms from said stripping zone at least a portion of said polyalkyltoluene, passing to an alkylation zone as an overhead from said stripping zone said olefin hydrocarbon in adrnixture with a molar excess based on said normally gaseous olefin hydrocarbon of .toluene to be alkylated, alkylating in an alkylation zone .said toluene with said olefin hydrocarbon in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from efiiuents of said alkylation zone unreacted toluene, monoalkyltoluene, and polyalkyltoluene, recycling the unreacted toluene for reiuse in the process, recovering monoalkyltoluene as prod- A.uct from the process, and recycling said polyalkyltoluene to the absorption zone as aforesaid.

In a still further embodiment the present invention relates to a combination process which comprises absorbing in an absorption zone a normally gaseous olefin hydrocarbon from a gas stream in a polyalkylxylene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed olefin hydrocarbon and said polyalkylxylene, removing from the process as bottoms from said stripping zone at least a portion of said polyalkylxylene, passing to an alkylation Azone as an overhead fromy said stripping zone said olefin hydrocarbon in. admixture :with -amolar excess based on ksaid normally gaseous olefin hydrocarbon of xylene to be alkylated, alkylating in the alkylation zone said xylene with said olefin hydrocarbon in the presence of an acidvacting alkylation catalyst at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted xylene, monoalkylxylene, and polyalkyl- `xylene, recycling the unreacted xylene for reuse in the process, recovering monoalkylxylene as product from the process, and recycling said polyalkylxylene to the absorption zone as aforesaid.

In a specific embodiment the present invention relates to a combination process which comprises absorbing in ,an absorption zone ethylene from a gas stream containing lminor quantities of ethylene in a polyethylbenzene at a .pressure of from about 100 to about 2000 pounds per 'square inch, passing to a stripping zone said absorbed .ethylene and said polyethylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylbenzene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of benzene to be alkylated, alkylating in the alkylation zone said benzene with said ethylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylation-alkyl transfer conditions, separating from efiiuents of said alkylation zone unreacted benzene, ethylbenzene, and polyethylbenzene, recycling the unreacted benzene for reuse in the process, recovering ethylbenzene as product from the process, and recycling said polyethylbenzene to the absorption zone as aforesaid.

This invention can perhaps be understood most readily by reference to the attached drawing. While of necessity certain limitations are introduced in such a description, no intention is meant to limit unduly the generally broad scope of this invention. As stated hereinabove, thefirst step of this combination process of the present invention comprises absorption in an absorption zone of an olefin hydrocarbon in a polyalkylaromatic hydrocarbon. The polyalkylaromatic hydrocarbon is characterized in that it has a higher boiling range than polyalkylaromatic hydrocarbon is the Vsame as is produced as a higher boiling alkylated aromatic hydrocarbon 4 product of the process. However, this polyalkylaromatic hydrocarbon utilized in theL absorption zone may be different from that produced in the process, particularly for start-up purposes. In the drawing, the first step of the process of this invention s represented as taking place in absorption zone 3. Absorption zone 3 is a conventional gas-liquid type of absorption zone familiar to those skilled in the art. It may be packed with various inert materials, or it may be equipped with trays and bubble caps, or it may be provided with means for spraying the liquid so that it will fall in a continuous spray while the gases to be absorbed pass upwardly therethrough and in contact therewith. To obtain best results, the absorption zone will be maintained at ambient temperatures and at a pressure of from about to about 2000 pounds per square inch or more. Higher temperatures may be utilized up to 100 C. or more although such temperaturesA are less desirable for increased gas solubility-in the liquid absorbent. With a normally gaseous olefin hydrocarbon such as ethylene, pressures within the higher portion of the above-mentioned range will preferably be utilized, that is, from about 1000 to about 2000 pounds per square inch. As the molecular weight of the normally gaseous olefin hydrocarbon utilized in this process increases, the pressure necessary to obtain satisfactory absorption in zone 3 may be reduced.

The olefin hydrocarbon reactant of the process, usually diluted by various unreactive gases such as hydrogen,

nitrogen, methane, ethane, propane, etc., is charged.

through lines 1 and 2 'to a lower section of absorption zone v3. The gas stream containing the olefin hydrocarbon to 'be utilized may be any refinery gas stream such as is obtained from a thermal cracking unit, a thermal reforming unit, a coking unit, a catalytic cracking unit, etc. Such refinery gas streams have in the past often been burned since an economical process for their.

Thus, a refinery off gas ethylene stream may contain varying quantities of methane and ethane while a refinery .off gas propylene stream is normally diluted with propane, and refinery off gas butene stream is normally diluted with butanes. A typical analysis in mol percent for a utilizable refinery off gas from a catalytic cracking unit is as follows: nitrogen, 4.0%; carbon monoxide, 0.2%; hydrogen, 5.4%; methane, 37.8%; ethylene, 10.3%; ethane, 24.7%; propylene, 6.4%; propane, 10.7%; and C4 hydrocarbons, 0.4%. The rate of addition of the vrefinery ofi gas through lines 1 and 2 to absorption zone 3 is controlled by the rate of addition of polyalkylaromatic hydrocarbon introduced to absorption zone 3 through line 4. That is, depending upon the temperature and pressure maintained in absorption zone 3, the rate of addition of the off gas through lines 1 and 2 is controlled so that sufficient olefin hydrocarbon is dissolved in the polyalkylaromatic hydrocarbon for utilization in the process as the alkylating agent therefor. The off gas,` as stated hereinabove, is generally introduced into a bottom section or zone of the absorption zone and the unabsorbed gases are vented therefrom through line 5 containing pressure controlled valves, etc., not shown. Furthermore, the pressure of the absorption zone and the rate of addition of the off gas can be controlled by continuous analysis of the vent gases from yline 5 so that the quantity of olefin hydrocarbons appearing in the vent gases in line 5 will be minimized.

The polyalkylaromatic hydrocarbon, produced as here- `vents recycle, when partially open recycles a portion of inafter.described, is introduced, preferably, rto the 'top section or portion of absorption zone-3 through Iline 4. The polyalkylaromatic hydrocarbon containing absorbed olen hydrocarbon passes downwardly through absorption zone 3 and is withdrawn therefrom via line 6 and 5 directed therethrough to stripping zone 7. As the polyalkylaromatic hydrocarbon descends through absorption zone 3, the normally gaseous olen hydrocarbon as well as other portions of the off gas are dissolved therein according to their solubilities at the temperatures and pressures maintained in this zone. These dissolved gases, as hereinabove `set forth, along with the polyalkylaromatic hydrocarbon are passed to stripping zone 7 wherein they are separated from the polyalkylaromatic hydrocarbon. These gases vpass overhead from stripping zone 7, are withdrawn therefrom through line 8, and pass through lines 10 and 12 to alkylation zone 13. Stripping zone 7 is of a conventional type and may be equipped with trays, packing, etc. This stripping zone is heated by reboiling a portion of the polyalkylaromatic hydrocarbon in a conventional type reboiler, not shown. The polyalkylaromatic hydrocarbon is Withdrawn from stripping zone 7 through lines 14 and 15 containing valve 16 and the net make of polyalkylarornatic hydrocarbon from the process is withdrawn therefrom through line 17. This will be explained `further hereinafter. The remainder of the polyalkylaromatic hydrocarbon necessary for utilization in absorption zone 3 as the absorber oil passes from ustripping zone 7 through lines 14 and 18 containing valve 19 through lines 20 and 4 back to absorption zone 3. It is readily seen that adjustment of valves 16 and 19 will result in more or less polyalkylaroma-tic hydrocarbon being withdrawn fromthe process and more or less poly- .alkylaromatic hydrocarbon being recycled back to absorption zone 3. These valves are normally adjusted, l

4as hereinabove `set forth, so that the net withdrawal through line 17 isJ equal to the net quantity of polyalkylaromatic hydrocarbon formed in alkylation zone 13. In another embodiment of this process, and as an additional advantage therefor, stripping zone 7 can be operated so that a portion of the polyalkylaromatic hydrocarbon goes overhead along with stripping zone gases. In this manner, a quantity of the polyalkylaromatic hydrocarbon can be passed back'to alkylation zone 13. This results in a suppression of the formation of additional polyalkylaromatic hydrocarbon in alkylation zone 13. Also, as will be set forth hereinafter, alkylation zone 13 is operated at alkylation-alkyl transfer conditions so that a portion of the alkyl groups on the polyalkylaromatic hydrocarbon are transferred to aroma-tic hydrocarbon to be alkylated, thus increasing the yield per pass of desired alkylaromatic hydrocarbon product. Furthermore, it also is within the generally broad scope of the invention to recycle a portion of the thus stripped gases containing rnormally gaseous olefin hydrocarbon from stripping zone 7 back to absorption zone 3. This is accomplis-hed lby means of line 36 containing valve 37 and line 38. The amount of these gases which are recycled is readily controlled yby control of valve 37 which when closed prethese gases, and when fully open recycles a fixed larger 0 portion of these gases. When valve 37 is maintained in a partially open or open position, the recycle gases are introduced to absorption zone 3 at a lower portion thereof than the off-gases are introduced thereto. A further i I beneficial effect 1s obtained 1n this method of operation 4since the absorbed gases leaving zone 3 will Kbe reliuxed any polyalkylaromatic hydrocarbon taken overhead therewith, passV through lines 8, 10, and 412 to alkylation'zone 7,5

13. Prior tol entry into alkylation zone- 13- they. `are joined with fresh aromatic hydrocarbon to be alkylated which is supplied to alkylation zone 13 via lines 11 and 12. Furthermore, unreacted aromatic hydrocarbon to be alkylated joins with these two streams from line 9 and passes through lines 10 and 12 to alkylation zone 13.v The quantityof aromatic hydrocarbon to be alkylated which is, supplied via line 11 is controlled by the total mols of alkylated aromatic hydrocarbon produced and withdrawn from the process through lines 34 and 17. Thus, if 1000 mols per hour of aromatic hydrocarbon in the form of desired alkylaromatic hydrocarbon and polyalkylaromatic hydrocarbon are withdrawn `through lines 34 and 17, 1000 mols of net fresh aromatic hydrocarbon will be charged to the process through lines Hand 12..

The aromatic hydrocarbon utilized in the process and supplied thereto through line 11 may be selected from various aromatic hydrocarbons and mixtures thereof including benzene, toluene, ortho-Xylene, meta-xylene, paraxylene, ethylbenzene, n-propylbenzene, cnmene, naphthalene, alpha-methylnaphthalene, beta-methylnaphthalene, etc. Of course, the process is most applicable to benzene hydrocarbons, and is more particularly applicable to those benzene hydrocarbons of high vapor pressure at normal conditions, particularly benzene and toluene. The net fresh aromatic hydrocarbon to be alkylated, unreacted and recycled aromatic hydrocarbon, absorbed gases, and any polyalkylaromatic hydrocarbon are passed in admixture from line 12 to alkylation zone 13. The process vis carried out so that the molar ratio of aromatic hydrocarbon to olefin hydrocarbon will be suicient to prevent polymerization of the olefin hydrocarbon prior to reaction thereof with the desired aromatic, hydrocarbon. The mol ratio utilized will generally-be greater-than 2:1 and in most cases will be greater than 3:1 but less than :1. In adjusting the mol ratio the excess alkyl groups on the polyalkylaromatic hydrocarbon must be taken into account for they will be transferred to fresh aromatic hydrocarbon in the alkylation zone. I

- Alkylation zone 13 is of the conventional type wherein the alkylation of the aromatic hydrocarbon with the vdissolved olen is effected. The mixture of aromatic hydrocarbon and olefin hydrocarbon, and polyalkylaromatic hydrocarbon, if any, is heated, preferably, (by means not shown) prior to passage thereof into the alkylation zone and thus the alkylation zone will comprise in this embodiment an adiabatic reactor. For example, the alkylation zone feed may be heat exchanged with the alkylation zone eiiluent andl then passed through a conventional type heater prior to passage into the alkylation zone. Alkylation zone 13 will contain an acid-acting alkylationalltyl transfer catalyst under suitable conditions of temperature, pressure, and reaction time, and thus the alkylation conditions utilized depend upon the particular acid-acting alkylation-alkyl transfer catalyst selected. The acid-acting catalyst may be selected ,from diverse materials such as and including sulfuric acid, phosphoric acid, hydrogen uoride, aluminum chloride, aluminum bromide, boron trifluoride, ferrie chloride, zinc chloride, zirconium chloride, various synthetically prepared socalled cracking catalysts such as silica-alumina, silicaalumina-zirconia, silica-magnesia, various acid-acting clays including activated alumina of commerce, Tonsil, Porocel, and what is known in the art as Solid Phosphoric Acid which is a calcin'ed composite of a phosphoric acid and a'siliceous adsorbent. With the utilization of such diverse materials as alkylation-alkyl transfer catalysts, the temperature utilized in the, alkylation zone will range from 0 about 0 C. or lower to about 450 C. or higher, preferably from about 50 to about 325 C.: The pressure utilized in the alkylation zone may vary from about'at- .mospheric to about 2000 pounds per square inch.. or more. In a batch type process the amount of catalyst in the alkylation zone may vary from-about 1% by Ato about 2 hours or more.

vweigh-t'based on the reactants to labout 500% by weight or more, and the residence time of the reactants in contact with these catalysts will vary from about 1 minute If the alkylation catalyst selected is a solid, such as solid phosphoric acid, or silicaalumina, the amount of catalyst utilized is ordinarily designated by means of hourly liquid space velocity thereover which may vary from 0.1 to about or more. In order to obtain high yields of monoalkylaromatic hy- `drocarbons, particularly monoalkylbenzene hydrocarbons, it is essential that the reaction mixture contain a substantial molar excess of aromatic hydrocarbon over olen hydrocarbon as set forth hereinabove.

Furthermore, with the hereinabove described acid-acting catalyst it is desirable to utilize conditions under which not only alkylation of the desired aromatic hydrocarbon with the olelin hydrocarbon takes place inthe alkylation zone, but alkyl transfer from polyalkylaromatic hydrocarbons to unalkylated aromatic hydrocarbons drawal of polyalkylaromatic hydrocarbon will be necessary. Furthermore, the elect ofthe polyalkylaromatic hydrocarbon in the alkylation zone will be to suppress the formation of larger amounts thereof in accordance with the law of mass action.

When the alkylation reaction has proceeded to the -desired extent, the products from the alkylation zone, also called alkylation zone eiuents, are withdrawn from alkylation zone 13 through line 21 to separator 22, which can also be termed the alkylation zone effluents receiver. Prior to passage of the alkylation zone effluents into separator 22 they are cooled, for example, by heat exchange with the alkylation zone charge, by means not shown. In separator 22 any unreactive gases which have been absorbed in absorption zone 3 are vented through lines 23 and 24 containing valve 25 to line 26 for uses not shown, for example, as fuel. If conversion of the olefin hydrocarbon in alkylation zone 13 is less than 100% so that recovery of unreacted olefin hydrocarbon becomes desirable, the vent gases can be passed from line A23 through line 27 containing valve 28 through line 29 back to line 2 for reabsorption of the olefius therefrom in absorption zone 3. Whether or not this is practical or leconomical not only depends upon the eiciency of ablsorption zone 3 but also depends upon the conditions utilized therein. Also, by control of valve 25 and valve 28, it is possible to vent a portion of these gases and to pass another portion thereof back to the absorption zone. ,In most cases, however, valve 28 is maintained in a 'closed position since the conditions in alkylation zone `10 will be adjusted for as near to 100% olefin consumption as practical, and therefore the only vent gases will be unreactive gases which were absorbed in absorption zone 3 along with the desired olefin hydrocarbon. Another reason for maintaining maximum olefin conversion in alkylation zone 13 is the molar excess of aromatic hydrocarbon to be alkylated maintained therein. If the amount of vent gas from separator 22 becomes too substantial,

'a portion of the aromatic hydrocarbon reactant, for ',example, benzene, will be lost in the vent gases because Yof the vapor pressure which the benzene exerts in separator 22. However, under proper operating conditions this amount of aromatic hydrocarbon, for example, benzene will be small. When the amount of gases becomes in. The liquid portion of the alkylation zone eliiuents is removed from separator 22 through line 30 and passed to fractionator 31 for recovery of unreacted aromatic hydrocarbon overhead therefrom. Fractionator 31 will be heated by a gas fired or steam reboiler, not shown. The unreacted aromatic hydrocarbon recovered in fractionator 31 passes overhead through lines 9, 10, and 12 back to alkylation zone 3 as aforesaid. Fractionator 31 is of a conventional type equipped with trays, bubble caps, or packing as the case may be. The reaction zone effluents higher boiling than the aromatic hydrocarbon to be alkylated are removed from fractionator 31 through line 32 and are passed to fractionator 33. Fractionator 33 Will be of a similar conventional type as set forth hereinabove in relation to fractionator 31. The desired alkylated aromatic hydrocarbon is removed overhead from fractionator 33 through line 34 from which it passes to storage or to other uses not shown. Line 34 is the means by which the net desired product is removed from the process. Such products include ethylbenzene, ethyltoluene, an ethylxylene, ethylcurnene, ethyl-n-propylbenzene, cumene, diisopropylbenzene, etc.

Polyalkylaromatic hydrocarbons higher boiling than the desired alkylaromatic hydrocarbon removed through line 34 are removed from fractionator 33 through line 35 and passed therefrom through line 4 to absorption zone 3 as aforesaid. The net make of polyalkylaromatic hydrocarbon can be withdrawn through line 17 as aforesaid. 'If the' net amount of polyalkylaromatic hydrocarbon is' greater than needed in absorption zone 3, and if the alkylation-zone 10 conditions have not been adjusted to obtain proper alkyl transfer, the net amount of polyalkylarornatic hydrocarbon in excess of that needed is removed from the process through line 17 and passed to storage or other uses not shown. As hereinabove pointed out, this amount is, in the preferred embodiment, maintained at a minimum, although in most cases the polyalkylaromatic hydrocarbons are high antiknock gasoline components.

The process utilized hereinabove has several advantages, all interrelated. First, recycle of polyalkylaromatic hydrocarbon suppresses further build-up by alkyl transfer from polyalkylaromatic hydrocarbon to aromatic hydrocarbon, and thus the yield of desired alkylaromatie hydrocarbon is increased. Second, the use of the polyalkylaromatic hydrocarbon as an absorber oil for the olefin hydrocarbons at once increases the effective olefin concentration, reduces the amount of inert gas handled in the alkylation zone and reduces the necessary size of the alkylation zone. Third, it provides a relatively non- Ivolatile absorber oil so that losses thereof as vapor in of the following example.

In this example ethylene from a dilute ethylene stream is reacted with benzene to produce barrels per day of ethylbenzene. The dilute ethylene stream or off-gas in the quantity of 53,600 standard cubic feet per hour passes through lines 1 and 2 to absorption zone 3. This off-gas contains 4.9 mol percent nitrogen, 0.2 mol percent carbon monoxide, 6.5 mol percent hydrogen, 45.9 mol percent methane, 12.5 mol percent ethylene, and 30.0 molv percent ethane. These gases are contacted with 10,000 liters per hour of diethylbenzene at a temperature of about 25 C. and a pressure of 1000 pounds per square inch. From vent line 5 passes 24,800 standard cubic feet ofgas per hour comprising 3300 mols per hour of nitrogen, 100 mols per hour of carbon monoxide, 4400 mols per hour of hydrogen, 20,300 mols per hour of methane, 950 mols per hour of =ethylene, and 2600 mols per hour of ethane. Of the gases passing `into absorption zone 3 89% of the ethane and ethylene are absorbed, 34.6% of the methane is absorbed, and none of the nitrogen, carbon monoxide, or hydrogen is absorbed. As a result of this absorption of ethylene in diethylbenzene, there is absorbed in the diethylbenzene which passes from absorption zone 3 through line 6 to stripping zone 7, 10,800 mols per hour of methane, 7550 mols per hour of ethylene, and 18,100 mols of ethane.

In stripping zone 7, operated at a 175 C. bottoms temperature and. at atmospheric pressure, these absorbed gases pass overhead through lines 8, 10, and 12 to alkylation zone 13. From the bottom of stripping zone 7 are withdrawn 610 mols per hour of diethylbenzene through lines 14 and 15 containing valve 16 to line 17. The

.remainder of the diethylbenzene Withdrawn via line 14 4by calcining a mixture of a phosphoric acid and kieselguhr. The alkylation of the benzene with the Yethylene is conducted at 290"4 C., 900 pounds per square inch, and at an hourly liquid space velocity of 1.5. The eiuents from alkylation zone 13 comprising methane, any unreacted ethylene, ethane, benzene, ethylbenzene, and diethylbenzene are passed through line 21 to highpressure separator 22. ln high pressure separator 22 are vented the unreactive and unreacted gases in a quantity of 10,800 mols per hour of methane, 910 mols per hour of ethylene, and 18,100 mols per hour of ethane. These gases are discharged from high pressure Separator 22 through lines 23, 24, and 26 containing valve 25. In this instance it is not feltthat reabsorption of these gases is economical since 88% of the ethylene charged to the reactor has been consumed.

The liquid products in high pressure separator 22 are passed therefrom through line 30 to fractionator 31 wherein the 24,170 mols per hour of benzene are fractionated overhead and recycled to the alkylation zone. From the bottom of fractionator 31 through line 32 is continuously withdrawn` the remaining liquid product which is fractionated in fractionator 33. 5,420 mols per hour of ethylbenzene as produced are removed from the process through line 34. This amount is equal to 100 barrels per day of the desired ethylbenzene.v From the bottom ot fractionator 33 are withdrawn 610 mols per hour of diethylbenzene which is recycled through lines 35 and 4 to absorption zone 3. To prevent build-up of high-boiling products in the process, the same quantity per hour of diethylbenzene and higher-boiling materials is removed from the process through line 17, as hereinabove set forth. f

I claim as my invention:

l. A combination process which comprises absorbing in an absorption zone a normally gaseous olefin hydrocarbon from a gas stream in a polyalkylaromatic hydro,-

carbon at a pressure of from about -l to about'2000 pounds per square inch, said polyalkylarornatic hydrocarbon being characterized by having a higher boiling range than the desired alkylated aromatic hydrocarbon product of the process, passing to a stripping zone said absorbed olefin hydrocarbon and said polyalkylaromatic hydrocarbon, removing from the process as bottoms from -said stripping zone at least a portion of said polyalkyl- -aromatic hydrocarbon, passing to an alkylation, zone as an overhead from said stripping zone said olefin hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of aromatic hydrocarbon to be alkylated, alkylating in the alkylation zone said aromatic hydrocarbon with said olelin hydrocarbon in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from efiluents of said alkylation zone unreacted aromatic hydrocarbon, desired alkylated aromatic `hydrocarbon product, and higher boiling polyalkylaromatic hydrocarbon, recycling the unreacted aromatic hydrocarbon for reuse in the process, recovering alkylated aromatic hydrocarbon as product from the process, and recycling said higher boiling polyalkylaromatic hydrocarbon to the absorption zone as absorbent for said normally gaseous olefin hydrocarbon. v i,

2. A combination process for producing an aromatic alkylate boiling in the gasoline range which comprises absorbing in an absorptionzone a normally gaseous olerin hydrocarbon` from a gas stream in a polyalkylaromatic hydrocarbon at a pressure of from about to about 2000 pounds per square inch, said polyalkylaromatic hydrocarbon being higher boiling than said alldate, passing to a stripping zone said absorbed olefin hydrocarbon and polyallrylaromatic hydrocarbon, removing from the process as a bottoms from said stripping zone at least a portion of said polyalkylaromatic hydrocarbon, passing to an alkylation zone as an overhead from said stripping zone said olefin hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of aromatic hydrocarbon to be alkylated, alkylating in the alkylation zone said aromatic hydrocarbon with said olefin hydrocarbon in the presence of an acid-acting alkylation catalyst atalkylation-alkyl transfer conditions, separating from efliuents of said alkylation zone unreacted aromatic hydrocarbon, monoalkylaromatic hydrocarbon, and higher boiling polyalkylaromatic hydrocarbon, recycling the unreacted aromatic hydrocarbon for reuse in the process, recovering monoalkylaromatic hydrocarbon as product from the process, and recycling said higher boiling polyalkylaromatic hydrocarbon to the absorption zone as absorbent for said normally gaseous olefin hydrocarbon.

3. A combination process which comprises absorbing in an absorption zone a normally gaseous olefin hydrocarbon from a gas stream in a polyalkylbenzene hydrocarbon at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed olefin hydrocarbon and polyalkylbenzene hydrocarbon, removing from the process as bottoms from said stripping zone at least a portion of said polyalkylbenzene hydrocarbon, passing to an alkylation zone as overhead from said stripping zone said olen hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of benzene hydrocarbon to be alkylated, alkylating in the alkylation zone said benzene hydrocarbon with said olefin hydrocarbon in the presence of an acid-acting allrylation catalyst at alkylation-alkyl transfer conditions, separating from efiiuents of said alkylation zone unreacted benzene hydrocarbon, monoalkylbenzene hydrocarbon, and polyallrylbenzene hydrocarbon, recycling the unreacted benzene hydrocarbon for reuse in the process, recovering monoalkylbenzene hydrocarbon as product from the process, and recycling said polyalkylbenzene hydrocarbon to the absorption zone as aforesaid.

4. A combination process which comprises absorbing in an absorption zone a normally gaseous olefin hydrocarbon from a gas stream in a polyalkylbenzene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed olefin hydrocarbon and said polyalkylbenzene, removing from the process as bottoms from said stripping zone at least la portion of said polyalkylbenzene, passing to an alkylation zone as an overhead from said stripping zone said olefin hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of benzene to be alkylated, alkylating in the alkylation zone said benzene with said olefin hydrocarbon in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted benzene, monoalkylbenzene, and polyalkylbenzene, recycling the unreacted benzene for reuse in the process, recovering monoalkylbenzene as product from the process, and recycling said polyalkylbenzene to the absorption zone as aforesaid.

5. A combination process which comprises absorbing inv an absorption zone a normally gaseous olefin hydrocarbon from a gas stream in a polyalkyltoluene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed olefin hydrocarbon and said polyalkyltoluene, removing from the process as bottoms from said stripping zone at least a portion of said polyalkyltoluene, passing to an alkylation zone as an overhead from said stripping zone said olefin hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of toluene to be alkylated, alkylating in the alkylation zone said toluene with said olefin hydrocarbon in the presence of an acid acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted toluene, monoalkyltoluene, and polyalkyltoluene, recycling the unreacted toluene for reuse in the process, recovering monoalkyltoluene as product from the process, and recycling said polyalkyltoluene to the absorption zone as aforesaid. 'I'

6. A combination process which comprises absorbing in an absorption zone a normally gaseous olefin hydrocarbon from a gas stream in a polyalkylxylene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed olefin hydrocarbon and said polyalkylxylene, removing from the process as bottoms from said stripping zone at least a portion of said polyalkylxylene, passing to an alkylation zone as an overhead from said stripping zone said olefin hydrocarbon in admixture with a molar excess based on said normally gaseous olefin hydrocarbon of xylene to be alkylated, alkylating in the alkylation zone said xylene with said olefin hydrocarbon in the presence of an acidacting alkylation catalyst at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted xylene, monoalkylxylene, and polyalkylxylene, recycling the unreacted xylene for reuse in the process, recovering monoalkylxylene product from the process, and recycling said polyalkylxylene to the absorption zone as aforesaid.

7. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethylbenzene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylbenzene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of benzene to be alkylated, alkylating in the alkylation zone said benzene with said ethylene in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from efiiuents of said alkylation `zone unreacted benzene, ethylbenzene, and polyethylbenzene, recycling the unreacted benzene for reuse in the process, recovering ethylbenzene as product from the process, and recycling said polyethylbenzene to the absorption zone as aforesaid.

8. A combination process which comprises absorbing ,in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethyltoluene lat a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethyltoluene, removing from the process as bottoms from said stripping zone at least a. portion of said polyethyltoluene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of toluene to be alkylated, alkylating in the alkylation zone said toluene with said ethylene in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from eiuents of said alkylation zone unreacted toluene, ethyltoluene, and polyethyltoluene, recycling the unreacted toluene for reuse in the process, recovering ethyltoluene as product from the process, and recycling said polyethyltoluene to the absorption zone as aforesaid.

9. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethylxylene at a pressure of from about to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethylxylene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylxylene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of xylene to be alkylated, alkylating in the alkylation zone said xylene with said ethylene in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted xylene, ethylxylene, and polyethylxylene, recycling the unreacted xylene for reuse in the process, recovering ethylxylene as a product from the process, and recycling said polyethylxylene to the absorption zone as aforesaid.

10. A combination process which comprises absorbing in an absorption zone propylene from a gas stream containing minor quantities of propylene in a polyisopropylbenzene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed propylene and said polyisopropylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyisopropylbenzene, passing to an alkylation zone as an overhead from said stripping zone said propylene in admixture with a molar excess based on said propylene of benzene to be alkylated, alkylating in the alkylation zone said benzene with propylene in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from efiluents of said alkylation zone unreacted benzene, cumene, and polyisopropylbenzene, recycling the unreacted benzene for reuse in the process, recovering cumene as product from the process, and recycling said polyisopropylbenzene to the absorption zone as aforesaid.

11. A combination process which comprises absorbing in an absorption zone propylene from a gas stream containing minor quantities of propylene in a polyisopropyltoluene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed propylene and said polyisopropyltoluene, removing from the process as bottoms from said stripping zone at least a portion of said polyisopropyltoluene, passing to an alkylation zone as an overhead from said stripping zone said propylene in admixture with a molar excess based on said propylene of toluene to be alkylated, alkylating in the alkylation zone said toluene with said propylene in the presence of an acid-acting alkylation catalyst at alkylation-alkyl transfer conditions, separating from effiuents of said alkylation zone unreacted toluene, propyltoluene, and polyisopropyltoluene, recycling the unreacted toluene for reuse in the process, recovering propyltoluene as product from the process, and recycling said polyisopropyltoluene to the absorption zone as aforesaid.

12. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethylbenzene at a pressure of from about 100 to about 2000 pounds per "13 square inch, passing to a stripping zone said absorbed ethylene and said polyethylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylbenzene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylc ne of benzene to be alkylated, alkylating in the alkylation zone said benzene with ethylene n the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylation-alkyl transfer conditions, separatlng from eluents of said alkylation zone unreacted benzene, ethylbenzene, and polyethylbenzene, recycling the unreacted benzene for reuse in the process, recovering ethylbenzene as product from the process, and recycling said polyethylbenzene to the absorption zone as aforesaid.

13. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containlng minor quantities of ethylene in a polyethyltoluene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethyltoluene, recovering from the process as bottoms from said stripping zone at least a portion of said polyethyltoluene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of toluene to be alkylated, alkylating in the alkylation zone said toluene with said ethylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted toluene, ethyltoluene, and polyethyltoluene, recycling said unreacted toluene for reuse in the process, recovering ethyltoluene as product from the process, and recycling at least a portion of said polyethyltoluene to the absorption zone as aforesaid.

14. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethylxylene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping Zone said absorbed ethylene and said polyethylxylene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylxylene, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of xylene to be alkylated, alkylating in the alkylation zone said xylene with said ethylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylation-alkyl transfer conditions, separating from effluents of said alkylation zone unreacted xylene, ethylxylene, and polyethylxylene, recycling the unreacted xylene for reuse in the process, recovering ethylxylene as a product from the process, and recycling said polyethylxylene to the absorption zone as aforesad.

l5. A combination process which comprises absorbing in an absorption zone propylene from a gas stream cotttaining minor quantities of propylene in a polyisopropylbenzene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed propylene and said polyisopropylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyisopropylbenzene passing to an alkylation zone as an overhead from said stripping zone said propylene in admixture with a molar excess based on said propylene of benzene to be alkylated, alkylating in the alkylation zone said benzene with said propylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylationalkyl transfer conditions, separating from efuents of said alkylation zone unreacted benzene, cumene, and polyisopropylbenzene, recycling the unreacted benzene for reuse in the process, recovering cumene as product from the process, and recycling said polyisopropylbenzene to the absorption zone as aforesaid.

16. A combination process which comprises absorbing in an absorption zone propylene from a gas stream containing minor quantities of propylene in a polyisopropyltoluene at a pressure of from about to about 2000 pounds per square inch, passing to a stripping zone said absorbed propylene and said polyisopropyltoluene, removing from the process as bottoms from said stripping zone said propylene in admixture with a molar excess based on said propylene of toluene to be alkylated, alkylating in the alkylation zone said toluene With said propylene in the pressure of a calcined composite of aphosphoric acid and a siliceous adsorbent at alkylationalkyl transfer conditions, separating from effluents of said alkylation zone unreacted toluene, propyltoluene, and polyisopropyltoluene, recycling the unreacted toluene for reuse in the process, recovering propyltoluene as.

product from the process, and recycling said polyisopropyltoluene to the absorption zone as aforesaid.

17. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethylbenzene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethylbenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylbenzene, recycling at least a portion of said absorbed and stripped ethylene from said stripping zone to the absorption zone as reflux therefor, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of benzene to be alkylated, alkylating in the alkylation zone said benzene Iwith said ethylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylation-alkyl transfer conditions, separating from efuents of said alkylation zone unreacted benzene, ethylbenzene, and polyethylbenzene, recycling the unreacted benzene for reuse in the process, recovering ethylbenzene as product from the process, and recycling said polyethylbenzene to the absorption zone as aforesaid.

18. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylene in a polyethyltoluene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethyltoluene, recovering from the process as bottoms from said stripping zone at least a portion of said polyethyltoluene, recycling at least a portion of said absorbed and stripped ethylene from said stripping zone to the absorption zone as reflux therefor, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of toluene to be alkylated, alkylating in the alkylation zone said toluene with said ethylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylationalkyl transfer conditions, separating from effluents of said alkylation zone unreacted toluene, ethyltoluene, and polyethyltoluene, recycling said unreacted toluene for reuse in the process, recovering ethyltoluene as product from the process, and recycling at least a portion of said polyethyltoluene to the absorption zone as aforesaid.

19. A combination process which comprises absorbing in an absorption zone ethylene from a gas stream containing minor quantities of ethylenei n a polyethylxylene at a pressure of fro-m about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed ethylene and said polyethylxylene, removing from the process as bottoms from said stripping zone at least a portion of said polyethylxylene, recycling at least a portion of said absorbed and stripped ethylene from said stripping zone to the absorption zone as reux therefor, passing to an alkylation zone as an overhead from said stripping zone said ethylene in admixture with a molar excess based on said ethylene of xylene to be alkylated, alkylating in the alkylation zone said xylene with said ethylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylationalkyl transfer conditions, separating from eluents of said alkylation zone unreacted xylene, ethylxylene, and polyethylxylene, recycling the unreacted Xylene for reuse in the process, recovering ethylxylene as product from the process, and recycling said polyethylxylene to the absorption zone as aforesaid.

20. A combination process which comprises absorbing in an absorption zone propylene from a gas stream containing minor quantities of propylene in a polyisopropylbenzene at a pressure of from about 100 to about 2000 pounds per square inch, passing to a stripping zone said absorbed propylene and said polyisopropyibenzene, removing from the process as bottoms from said stripping zone at least a portion of said polyisopropylbenzene, recycling at least a portion of absorbed and stripped propylene from said stripping Zone to the absorption zone as reflux therefor, passing to an alkylation zone as an overhead from said stripping zone said propylene in admixture `with a molar excess based on said propylene of benzene to 'be alkylated, alkylating in the alkylation zone said benzene with said propylene in the presence of a calcined composite of a phosphoric acid and a siliceous adsorbent at alkylation-alkyl transfer conditions, separating from eluents of said alkylation zone unreacted benzene, cumene, and polyisopropylbenzene, recycling the unreacted ybenzene for reuse in the process, recovering cumene as product from the process and recycling said polyisopropylbenzene to the absorption zone as aforesaid.

21. A process for producing an aromatic alkylate lwhich comprises contacting a gas stream containing a normally gaseous oletin with a polyalkylaromatic hydrocarbon absorbent of higher boiling point than said alkylate under conditions to absorb normally gaseous olen in said absorbent, stripping the absorbed olefin from the enriched absorbent and commingling therewith an alkylatable aromatic hydrocarbon, subjecting the resultant mixture to alkylation to react the olefin with the last-named hydrocarbon, separating from the resultant products said aromatic alkylate and higher boiling polyalkylaromatic hydrocarbon, and supplying at least a portion of the latter to the aforesaid contacting step as said polyalkylaromatic hydrocarbon absorbent.

22. The process of claim 21 further characterized in that a portion of the polyalkylaromatic hydrocarbon is stripped from said enriched absorbent together with the olefin and supplied to the alkylating step.

References Cited n the le of this patent UNITED STATES PATENTS 2,381,175 MattoX Aug. 7, 1945 2,396,682 Carmody Mar. 19, 1946 2,403,879 Schulze et al. July 9, 1946 2,439,080 Davies Apr. 6, 1948 2,465,610 Short et al Mar. 29, 1949 2,498,567 Morris et al Feb. 21, 1950 

1. A COMBINATION PROCESS WHICH COMPRISES ABSORBING IN AN ABSORPTION ZONE A NORMALLY GASEOUS OLEFIN HYDROCARBON FROM A GAS STREAM IN A POLYALKYLAROMATIC HYDROCARBON AT A PRESSURE OF FROM ABOUT 100 TO ABOUT 2000 POUNDS PER SQUARE INCH, SAID POLYALKYLAROMATIC HYDROCARBON BEING CHARACTERIZED BY HAVING A HIGHER BOILING RANGE THAN THE DESIRED ALKYLATED AROMATIC HYDROCARBON PRODUCT OF THE PROCESS, PASSING TO A STRIPPING ZONE SAID ABSORBED OLEFIN HYDROCARBON AND SAID POLYALKYLAROMATIC HYDROCARBON, REMOVING FROM THE PROCESS AS BOTTOMS FROM SAID STRIPPING ZONE AT LEAST A PORTION OF SAID POLYALKYLAROMATIC HYDROCARBON, PASSING TO AN ALKYLATION ZONE AS AN OVERHEAD FROM SAID STRIPPING ZONE SAID OLEFIN HYDROCARBON IN ADMIXTURE WITH A MOLAR EXCESS BASED ON SAID NORMALLY GASEOUS OLEFIN HYDROCARBON OF AROMATIC HYDROCARBON TO BE ALKYLATED, ALKYLATING IN THE ALKYLATION ZONE SAID AROMATIC HYDROCARBON WITH SAID OLEFIN HYDROCARBON IN THE PRESENCE OF AN ACID-ACTING ALKYLATION CATALYST AT ALKYLATION-ALKYL TRANSFER CONDITIONS, SEPARATING FROM EFFLUENTS OF SAID ALKYLATION ZONE UNREACTED AROMATIC HYDROCARBON, DESIRED ALKYLATED AROMATRIC HYDROCARBON PRODUCT AND HIGHER BOILING POLYALKYLAROMATIC HYDROCARBON FOR RECYCLING THE UNREACTED AROMATIC HYDROCARBON FOR REUSE IN THE PROCESS, RECOVERING ALKYLATED AROMATIC HYDROCARBON AS PRODUCT FROM THE PROCESS, AND RECYCLING SAID HIGHER BOILING POLYALKYLAROMATIC HYDROCARBON TO THE ABSORPTION ZONE AS ABSORBENT FOR SAID NORMALLY GASEOUS OLEFIN HYDROCARBON. 